added typing stubs for scienceplots

src/scienceplots-stubs/__init__.pyi

+#!/usr/bin/env python3
+"""
+Init-file for the stub-file for the library SciencePlots, which is a dependency
+of scientific_plots. This library must only be imported, but remains unused in
+the code, except for the added "science" style. Thus, this module does not
+actually contain any functions or classed.
+"""